A group of 83 two-to-eighteen-week-old chickens with acute infectious hepato-myelopoietic disease (a German form of inclusion-body-hepatitis) were observed to have the following histologic lesions: panmyelophthisis, small foci of liver necrosis, often with intranuclear inclusion bodies in hepatocytes (15 to 20% of chickens), involution-like atrophy of the bursa of Fabricius and thymus, loss of lymphatic tissue in spleen and cecal tonsils, and nonpurulent myocarditis. In 18 survivors 6 to 8 weeks after clinical signs of disease, nonpurulent myocarditis but normal lymphatic organs and bone marrow were present. A group of 75 chickens were infected after hatching with the field isolant "1942." Between the 3rd and 9th weeks postinoculation the same histologic changes-though mostly milder-were demonstrated. This syndrome differs somewhat from the syndrome described as inclusion body hepatitis in America and Europe.